I voted for Mayonaka no Shadow Boy cos School Kakumei is awesome!
& Yabu wrote it, which makes it even nicer!
I would've voted for Ultra Music Power cos Star Time's my favourite hsj song,
but I'm listening to School Kakumei now, so I didn't think ^^

I voted for Ultra Music Power since it's their first single. And they were really awesome to think that they were so young back then. And it was the song that made them NO. 1 all together. Also, IT WAS THE REASON WHY I STARTED TO LOVE HEY SAY JUMP. The first ever video where I've seen them. AND YUTOOO. XD

mayonaka no shadow boy~!!cus i lik their dance in e PV and their singing too~i lik all e songs actually becus they keep improving in their singing and dance in every new songs they going to produce...haha

well, i liked all of their songs so it was really hard to decide.... ultra music power made them famous, dreams come true is plain cute, your seed has some ttly AWESOME dancing, and they all look EXTREMELY hot in mayonaka no shadow boy.....i like star time 2, though u didnt list it......
chose your seed cause i felt like it..... if i could i'd vote for them all

If it's single you're talking about..
I like Ultra Music Power the best!!
with raps of Hikaru and the high pitch of Chii overheard.. simply awesome!!
but if it's the mv.. it's definitely Mayonaka no Shadow Boy!!
all of them are hot there!! especially my ichiban!! Yamada!!

I voted for UMP though because the meaning of the song is better than Shadow boy's.. xDD
it's like..they talked about Cherry the whole time in Shadow Boy!! xDD